Foaming resin is commonly used as material for seat cushion of a vehicle seat.
Hardness and repulsion of cushion foam (so called “seat cushion”) will be changed by body weight and preference of the occupants.
As for commercial vehicles used for sales activities, for example, unspecified numbers of drivers often drive the same vehicle and they sometimes argue hardness of the cushion foam.
In this case, if the hardness of the cushion foam can be adjusted, it can not only satisfy the preference of the drivers but also can contribute to decreasing their work loads.
Although hardness of cushion foam made from foaming resin can be adjusted by the foam size and the foaming ratio, its hardness cannot be adjusted once the cushion foam is formed.
FIG. 11 is the sectional view of a seat cushion 10J which is an example of one of the possible structures to adjust the hardness of the cushion foam.
FIG. 11 shows the seat cushion 10J which comprises a cushion foam 1, a cushion trim cover 2 and a cushion pan 3. Also, there is a rigid plate member 40 below the lower surface 1b of the cushion foam 1.
This plate member 40, for example, suppresses shape change of the lower surface 1b of the cushion foam 1 when the occupant bounces while seated, so as to adjust the hardness of the cushion foam indirectly.
Since the shape of the plate member 40 cannot follow the irregularity at the reinforcing rib 3t of the cushion pan 3 in the structure shown in FIG. 11, the plate member 40 is inclined as shown in FIG. 12.
The cushion foam 1, therefore, may be set in an inclined state.
Moreover, since abnormal sound is heard every time the rigid plate member 40 contacts with the (reinforcing rib 3t of the) steel cushion pan 3, it may give discomfort to the seated occupant of the vehicle.
As for another prior art, an invention is proposed to make a cavity in the cushion and a movable plate is provided in the cavity to adjust the cushion foam (refer to the Patent Literature 1).
This prior art, however, is intended for the hardness adjustment of the cushions of furniture chairs and cannot be applied to the cushions of vehicle seats.